FIELD OF THE INVENTION
The invention relates to a method for checking heat exchanger tubes made of metallic material.
Heat exchangers and especially heat exchanger tubes disposed in the heat exchanger are regularly checked with nondestructive test methods as to their condition. One of those test methods is the eddy-current integrity test which is known as such. That test makes it possible to recognize even very minor defects or damages in a tube, for example cracks, which penetrate only slightly into the tube wall and which cannot yet cause a leak. It is necessary to recognize such small cracks at an early stage, especially for heat exchangers which are part of a nuclear power plant, in order to prevent a leak.
It was found that the accuracy of the defect detection in the eddy-current integrity test decreases during the course of the operating time. Furthermore, it was found that in the course of the operating time the heat exchange also decreases.